Yes I have been thinking about the dolly too - no work on it yet though.

S thanks for the post, I have the same EDF motor and that ESC as well, both are top notch (they run in my CMP T-45 with a WeMoTec Midifan). The ESC is very well made, Hobbywing, and easy to program with the box. The HK EDF motor runs cool in EDF at 1500-2000W .

What is you CG, measured at where the wing meets the fuse? I see your wingspan is 135cm = 53'', whereas ours is 154cm = 63'' - so ours is just 14% slightly larger.

It is very interesting that you run such a small prop, I think most outrunners will fly apart and/or destroy the bearings past 15k, hence the need for an inrunner...

The video is impressive

Hi
The CG is 140 mm, measured at where the wing meets the fuse.
And it feel perfekt.

I also think of a dolly, but I dont have rudder, so it can be a challenge.
Motor and prop test will come soon

SK3 1900kv EDF motor

I wish I had a semi-scientific criterion to decide what prop size & pitch to put on this thing.

My feeling is that many Me-163 setups use a prop that is WAY too large, at least for my taste. It seems people often just take over what worked well / flew well in a P-51 or Corsair and transfer it to the Me-163 ... Coming from the EDF world, where "props" are tiny in diameter, one would be inclined to think small(er). The same would follow if one were to think of an F5D type setup.

A simple back-of-the-envelope calculation (for my Me-163B, other sizes would have to be recalculated) would lead me to the following considerations:

Let's say I want ca. 300W/lb which will give a good performance envelope. Since the weight rtf is in the 8lbs (3.6kg) region with some good sized batteries, that would limit the setup to ca. 2400W. Since I don't want to use overly exotic ESC's, I will use (2400W/100A) = 24V or let's say conservatively an 8S = 4S+4S setup (6S is a bit marginal).

Also, let's say that I want the (max, level) flying speed to be in the 150mph (240km/h) region.

b) the 9x9 pitch speed (178mph) is probably excessive, and a lot of prop air will juts dissipate in heat and turbulent wake.

c) that 11x11 and 10x10 should work.

Now, there's another variable in the equation, and that's the airframe drag. It will increase as velocity^2, and at flying speed (the desired 150mph) thrust=drag.

Since the Me-163 airframe is a bit draggy (it definitely does not look like an F5D airframe!) at some point without sufficient prop thrust
it will stop to accelerate.

I don't have a good way of computing the Me-163's airframe drag, but I am guessing that the drag could make the choice swing towards the larger, 11x11 prop. Since drag in these models is largely proportional to the total surface area, I could compare the Me-163 to some other airframe where the drag is known, and then scale the results by the ratio of surface areas ...

I have not taken further effects (such as prop unloading) into account as I did not know how to account for those (-10% rpm at
flying speed?), but it seems the above very simplistic arguments seem to suggest that a 11x11 or 10x10 prop should be in the right ballpark...

Nice analysis. The one thing that struck me about my K&A Komet is the speed with a relatively modest set-up. While the airframe is portly, I think the drag due to flow separation along the air frame is probably pretty low. Of course that is compared to other speed 400/480 sized aircraft which aren't all that streamlined.

In the book I am reading (quoted above) by an Me-163 pilot he points out two interesting facts.

One is that Messerschmitt did not want to build any more Me-163B's in 1944, the ministry of air applied some pressure on them to continue; it seems they (M) thought much more highly of the Me-262.

The second interesting thing is that seasoned fighter pilots like the author found out that in a slow turn, like the one on landing approaches, the Me-163 would easily get into a unrecoverable deadly spin.

The reason is simple: To make a turn in a tail-less airfcraft, you give it aileron and then up elevator. The latter acts like spoilerons and dumps lifts, the result can be flow separation and a stalled wing.

The cure was to instruct all Me-163 pilots to use plenty of rudder to make a slow turn ...